Thanks! Yes, I think this would fit well as a CoC sandbox adventure, lots of cosmic horror inspiration here for sure.
Closest movie inspiration would be Invasion of the Body Snatchers (1978), but set in the early 1800s, or in a remote town that has not modernized. I had watched Midnight Mass (2021) prior to writing this too, probably influenced the creepy church and small community vibe.
Depends on your usual session duration, but 2-4 evenings, I’d say. It’s a small hex area, travel is pretty quick, but lots opportunities for distraction. Side hooks outside the main adventure and NPC interactions could stretch things out, if your players dig into that kind of thing. :]